Hello everyone, I have a nearly perfect 111K mileage 2003 S type base 4.2 with the same problems described above. On cold start, it idles rough, chugs sometimes, and sometimes sets a CEL with "limited performance" but not always. I get codes for lean fuel mixture right and left when the CEL comes on. When I clear the codes it runs like new again. When the engine is warm it runs perfectly. I let it idle for a few minutes upon cold starts and it will sometimes line itself out without setting a code or CEL. Other times not. Brakes are only affected on the first use when cold.

I have had the vacuum lines for leaks with smoke and find no leaks. I have also tried carb cleaner and found no leaks, or at least no drop in RPM.

The spark plugs and coils were replaced about a year ago, and has only had about 3000 miles on it since then. Notably, it was not having this issue before or after this was done. The problem started about 4 months ago and we have driven the car very little since then.

The throttle body was replaced, the intake gaskets were replaced, the engine temp sensor was replaced, the MAF sensor was replaced, and no change.

It has been to a highly recommended shop that supposedly specializes in Jaguar (they replaced the throttle body saying it was cracked along with the heater valves) and after $2600, no change.

I'm kind of at a dead end.

Anyone have any other ideas? Please help!

 

Maybe check the intake plastic bellows for cracks? They can be invisible and we just had a long thread where the problem finally turned out to be leaks in the intake bellows.
I don't see where you changed the fuel filter??
Also with the miles you have the fuel pump is suspect? Can you read the fuel pressure? Your car should have a Schrader test point on the passenger side at the rear of the engine.

Please post the actual codes as we really must see exactly what the car is throwing??
Unless there was a MAF code we don't know if that was needed or not?
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@Ricksjagg, use a smart phone with the Torque app to connect to the vehicle's PCM via the OBD port with a Bluetooth interface to read the STFTs and LTFTs when the performance issue occurs. Post the results here.

+1 on also using the Torque app to read fuel pressure. Fuel pressure should be around 3 bar (300 kPa) during start up and idle, and around 3.8 bar (380 kPa) at WOT.

If the MIL is on, post the actual DTCs here as well.

 

IMO.... do a pressure check on the cooling system and check the engine oil for coolant contamination. (there is a chemical test you can do yourself)